Properties of an n+ i p+ Semiconductor Detector

A semiconductor nuclear particle detector fabricated by alloying or diffusing p+ layers and n+ layers into opposite faces of a slab of very high resistivity p-type silicon results in a device with several advantages over the conventional semiconductor detector structure. In the n+ i p+ structure, the space charge region extends throughout the entire silicon wafer upon application of a few volts bias and since further increases in bias do not appreciably change the width of the space charge region, the capacitance approaches a constant value. The series resistance of such a structure is very low and the collection time is exceedingly short, limited only by the applied field and the high field mobility of the carriers. Experimental data on collection time versus applied bias for several different nuclear particles as well as the characteristics of the unit in a low noise detector-amplifier system are presented.